U.S. patent number 6,454,716 [Application Number 09/577,385] was granted by the patent office on 2002-09-24 for system and method for detection of fetal heartbeat.
This patent grant is currently assigned to P.M.G. Medica Ltd.. Invention is credited to Jona Zumeris.
United States Patent |
6,454,716 |
Zumeris |
September 24, 2002 |
System and method for detection of fetal heartbeat
Abstract
The present invention provides a device and method for
monitoring and detecting a fetal heartbeat that can be employed by
ordinary people with minimal, if any, training, such as expectant
mothers. The device can monitor and detect a fetal heartbeat with
minimal positioning along the female body at the pregnant portion
(the womb) as the device is configured to transmit and receive
energy waves at wide angles. The device is economical and is
preferably designed for domestic use, outside of the hospital or
clinical setting. Specifically, the invention is based on a unique
configuration of piezoelectric elements in cooperative
configuration with a series of oscillators that is able to transmit
and receive ultrasonic waves simultaneously The configuration
allows for an optimal scanning range at an unlimited number of
angles.
Inventors: |
Zumeris; Jona (Nesher,
IL) |
Assignee: |
P.M.G. Medica Ltd. (Nesher,
IL)
|
Family
ID: |
24308477 |
Appl.
No.: |
09/577,385 |
Filed: |
May 23, 2000 |
Current U.S.
Class: |
600/453 |
Current CPC
Class: |
A61B
8/02 (20130101); A61B 8/0866 (20130101); A61B
8/4281 (20130101); A61B 8/4461 (20130101); A61B
8/4483 (20130101); G01S 15/8938 (20130101); G01S
15/8979 (20130101) |
Current International
Class: |
A61B
8/00 (20060101); A61B 8/02 (20060101); G01S
15/89 (20060101); G01S 15/00 (20060101); A61B
008/02 () |
Field of
Search: |
;600/437,438,453-456,459 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jaworski; Francis J.
Attorney, Agent or Firm: Eitan, Pearl, Latzer &
Cohen-Zedek
Claims
What is claimed is:
1. Apparatus for transmitting and receiving energy waver
comprising: at least one piezoceramic scanner in communication with
a first oscillator; at least one piezoceramic transmitter in
communication with a second oscillator and operatively coupled to
said piezoceramic scanner; and at least one piezoceramic receiver
operatively coupled to said piezoceramic scanner, wherein said
piezoceramic transmitter is configure to transmit waves to an
object, said receiver is configured to receive signals from said
object, and said piezoceramic scanner is configured to vibrate so
as to provide a wide scanning area of said object.
2. The apparatus of claim 1 wherein said first oscillator and said
second oscillator are configured for operation based on a
sinusoidal wave input.
3. The apparatus of claim 1 wherein said first oscillator and said
second oscillator are configured for operation based on a standing
wave input.
4. The apparatus of claim 1 wherein said scanner is a piezoceramic
plate.
5. The apparatus of claim 1 wherein said scanner is a piezoceramic
disc.
6. The apparatus of claim 1 wherein said scanner includes a
piezoceramic torsional element.
7. The apparatus of claim 1 wherein said scanner, said transmitter
and said receiver are coupled so as to oscillate
simultaneously.
8. The apparatus of claim 1 wherein said scanner, said transmitter
and said receiver are coupled so as to oscillate simultaneously at
a second mode of oscillation.
9. The apparatus of claim 1 wherein said at least one piezoceramic
trasmitter and at least one piezoceramic receiver are configured in
various shapes to achieve variability in scanning.
10. The apparatus of claim 1 wherein said at least one piezoceramic
transmitter and said at least one piezoceramic receiver are
configured to transmit and receive waves in a perpendicular
direction with respect to said scanner.
11. The apparatus of claim 1 additionally comprising a filter layer
operatively coupled to said scanner.
12. The apparatus of claim 11 wherein said filter layer has a
thickness of approximately 1/4 the wavelength of said energy waves
transmitted by said at least one piezoceramic transmitter.
13. The apparatus of claim 1 wherein said at least one piezoceramic
transmitter includes multiple piezoceramic transmitter
elements.
14. The apparatus of claim 1 wherein said at least one piezoceramic
receiver includes multiple piezoceramic receiver elements.
15. A system for detecting a fetal heartbeat comprising: at least
one piezoceramic transmitter; at least one piezoceramic receiver;
at least one piezoceramic scanner operatively coupled, to said at
least one piezoceramic transmitter and said at least one
piezoceramic receiver; a processor in communication with said
scanner, said transmitter and said receiver, wherein said processor
comprises a first oscillator in communication with said scanner and
a second oscillator in communication with said transmitter wherein
said first oscillator is configured to vibrate said piezoceramic
scanner and said second oscillator is configured to transmit waves
to said object; and an amplifier unit in communication with said
piezoceramic receiver, said amplifier unit configured for
converting said received waves into an output signal.
16. The system of claim 15 wherein said first oscillator and said
second oscillator are configured for operation based on a
sinusoidal wave input.
17. The system of claim 15 wherein said first oscillator and said
second oscillator are configured for operation based on a standing
wave input.
18. The system of claim 15 wherein said at least one scanner
includes a piezoceramic disc.
19. The system of claim 15 wherein said at least one scanner
includes a piezoceramic plate.
20. The system of claim 15, wherein said at least one scanner
includes a piesoceramic torsional element.
21. The system of claim 15 wherein said at least one piezoceramic
transmitter and said at least one piezoceramic receiver are
configured in various shapes to achieve variability in
scanning.
22. The apparatus of claim 15 wherein said scanner, said
transmitter and said receiver are coupled so as to oscillate
simultaneously.
23. The apparatus of claim 15 wherein said scanner, said
transmitter and said receiver are coupled so as to oscillate
simultaneously in a second mode of oscillation.
24. The system of claim 15 wherein said output signal is in the
form of audio output via speaker.
25. The system of claim 15 wherein said output signal is in the
form of digital display via counter.
26. The system of claim 15 wherein said at least one piezoceramic
transmitter and said at least one piezoceramic receiver are
configured to transmit and receive waves in a perpendicular
direction with respect to said scanner.
27. The system of claim 15 additionally comprising a filter layer
operatively coupled to said scanner.
28. The system of claim 27 wherein said filter layer has a
thickness of approximately 1/4 the wavelength of said energy waves
transmitted by said at least one piezoceramic transmitter.
29. The system of claim 15 wherein said at least one piezoceramic
transmitter includes multiple piezoceramic transmitter
elements.
30. The system of claim 15 wherein said at least one piezoceramic
receiver includes multiple piezoceramic receiver elements.
31. A method for detecting a fetal heartbeat comprising the steps
of: providing at least one piezoceramic transmitter, at least one
piezoceramic receiver, and at least one piezoceramic scanner
operatively coupled to said at least one piezoceramic transmitter
and said at least one piezoceramic receiver; energizing said
scanner by a first oscillator, simultaneously energizing said
piezoceramic transmit by a second oscillator so as to create a
scanning range over a predetermined while transmitting mechanical
waves; and receiving signals over said predetermined arc, said
signals corresponding to a fetal heartbeat.
32. The method of claim 31 additionally comprising the step of
varying the scanning sequence.
33. The method of claim 32 wherein the step of varying he scanning
sequence is accomplished by varying a voltage input.
34. The method of claim 32 wherein the step of varying the scanning
sequence is accomplished by varying frequency input.
35. The method of claim 32 wherein the step of varying the scanning
sequence is accomplished by varying a wave input.
36. The method of claim 31 wherein the step of energizing includes
inputting a continuous signal.
37. The method of claim 31 wherein the step of energizing includes
inputting a pulsed signal.
38. The method of claim 31 wherein the step of energizing includes
inputting several signals for progressive wave scanning.
39. A piezoceramic scanner coupled to a transmitter and a receiver
and in communication with a first oscillator wherein said first
oscillator is configured to transmit electrical waves to said
piezoceramic scanner, and wherein said electrical waves are
transformed into mechanical waves within said piezoceramic scanner,
said mechanical waves configured to vibrate said piezoceramic
scanner.
Description
FIELD OF THE INVENTION
The present invention relates to heart rate detection and in
particular to devices for monitoring and detection of fetal
heartbeat.
BACKGROUND OF THE INVENTION
Detection of fetal heartbeat has been an important indicator of the
health of a fetus and is routinely performed by health
professionals. Additionally, the expectant mother and others around
her are also interested in detecting and hearing this
heartbeat.
Devices used for fetal heartbeat detection and monitoring by health
professionals are such that their operation typically requires
substantial medical training For example, operation of these
devices involves manually moving the head containing the
transmitter and receiver until the heartbeat is detected. This is
because these devices typically employ ultrasonic waves that are
transmitted from and received by the device in a "straight line"
manner.
Also, these devices may be of a size so as to be limited to
hospital or other clinical settings. Moreover, these devices are
expensive and not suitable for home or domestic use by ordinary
individuals.
Devices suitable for home or domestic usage are available, for
example a portable ultrasonic doppler system described in U.S. Pat.
No. 4,413,629, a fetal heart detector described in U.S. Pat. No.
4,413,629, a transducer for extra-uterine monitoring of fetal heart
rate described in U.S. Pat. No. 4,966,152 and a Biophysical Fetal
Monitor as described in U.S. Pat. No. 5,817,035. However, these
devices are expensive and like the professional devices require the
user to manually move portions of the device to locate the
heartbeat, as these devices also operate in the fetal straight-line
manner. Alternatively, a multiple array of sensors is used to
achieve adequate coverage in order to locate the fetal heart.
SUMMARY OF THE INVENTION
The present invention provides a device and methods for monitoring
and detecting a fetal heartbeat that can be employed by ordinary
people with minimal, if any, training. The device can monitor and
detect a fetal heartbeat with minimal positioning along the female
body at the pregnant portion (the womb) as the device is configured
to transmit and receive energy when at wide angles. The device is
economical and is preferably designed for domestic use, outside of
the hospital or clinical setting.
The present invention relates to an apparatus for scanning and
receiving energy waves having at least one piezoelectric
transmitter, at least one piezoelectric receiver, and at least one
support member for the transmitter and receiver. The support member
is operatively coupled to at least one piezoelectric transmitter
and at least one piezoelectric receiver for oscillating
synchronously over a predetermined range of voltages and
frequencies and transceiving energy waves over a predetermined
angular range.
In a further embodiment the present invention also includes at
least one oscillator in communication with the support member, for
vibrating the support member. Typically, the oscillator is
configured for operation based on a sinusoidal wave input or based
on a standing wave input. However, other wave types are possible as
well.
In a further embodiment of the present invention, the apparatus
also has at least one oscillator in communication with the
piezoelectric transmitter, for vibrating the piezoelectric
transmitter. Typically, the oscillator is configured for operation
based on a sinusoidal wave input or on a standing wave input.
although other wave types are possible as well,
In a further embodiment of the present invention, the apparatus as
described hereinabove further includes at least one activatable
vibrating element in communication with the support member, whereby
the element is configured for communication with the piezoelectric
transmitter and piezoelectric receiver to achieve variability in
scanning. The activatable vibrating element may be a piezoelectric
disc, plate or torsional element or any other configuration.
Typically, the support member comprises piezo-ceramic material.
The piezoelectric transmitter and piezoelectric receiver may be
configured in various shapes to achieve variability in scanning.
Further, the piezoelectric transmitter and piezoelectric receiver
may comprise piezo-ceramic material.
In a further embodiment of the present invention, the piezoelectric
transmitter and piezoelectric receiver may be configured to vibrate
in a perpendicular direction with respect to the support
member.
In one embodiment of the present invention, the apparatus may
additionally include one or more filter layers operatively coupled
to the support member. This filter layer may have a thickness of
approximately 1/4 the wavelength of the energy waves transmitted by
the piezoelectric transmitter.
The at least one piezoelectric transmitter may, include one
piezoelectric transmitter or multiple piezoelectric transmitter
elements. Similarly, the at least one piezoelectric receiver may
include one piezoelectric receiver or multiple piezoelectric
receiver elements. Further, the at least one support member may
comprise individually activatable sections.
The present invention further relates to a system for detecting a
fetal heartbeat having at least one piezoelectric transmitter, at
least one piezoelectric receiver, at least one support member for
the transmitter and receiver, and an amplifier unit. The support
member is operatively coupled to at least one piezoelectric
transmitter and at least one piezoelectric receiver for oscillating
synchronously over a predetermined range of voltages and
frequencies and transceiving energy waves over a predetermined
angular range. The amplifier unit in communication with the
piezoelectric transmitter is configured for converting the received
energy waves into an output signal.
In a further embodiment the present invention also comprises at
least one oscillator in communication with the support member, for
vibrating the support member. Typically, the oscillator is
configured for operation based on a sinusoidal wave input or based
on a standing wave input. However, other wave types are possible as
well.
In a further embodiment of the present invention, the system also
has at least one oscillator in communication with the piezoelectric
transmitter, for vibrating the piezoelectric transmitter.
Typically, the oscillator is configured for operation based on a
sinusoidal wave input or on a standing wave input, although other
wave types are possible as well.
In a further embodiment of the present invention, the system as
described hereinabove further includes at least one activatable
vibrating element in communication with the support member, whereby
the element is configured for communication with the piezoelectric
transmitter and piezoelectric receiver to achieve variability in
scanning The activatable vibrating element may be a piezoelectric
disc, plate or torsional element, or any other configuration.
Typically, the support member comprises piezo-ceramic material.
The piezoelectric transmitter and piezoelectric receiver may be
configured in various shapes to achieve variability in scanning.
Further, the piezoelectric transmitter and piezoelectric receiver
may comprise piezo-ceramic material.
In one embodiment of the present invention, the output signal is in
the form of audio output via speaker. In another embodiment of the
present invention, the output signal is in the form of digital
display via counter.
In a further embodiment of the present invention, the piezoelectric
transmitter and piezoelectric receiver may be configured to vibrate
in a perpendicular direction with respect to the support
member.
In one embodiment of the present invention, the system may
additionally include one or more filter layers operatively coupled
to the support member. This filter layer may have a thickness of
approximately 1/4 the wavelength of the energy waves transmitted by
the piezoelectric transmitter.
The at least one piezoelectric transmitter may include one
piezoelectric transmitter or multiple piezoelectric transmitter
elements. Similarly, the at least one piezoelectric receiver may
include one piezoelectric receiver or multiple piezoelectric
receiver elements. Further, the at least one support member may
comprise individually activatable sections.
The present invention further relates to a method for detecting a
fetal heartbeat including the steps of providing at least one
piezoelectric transmitter, at least one piezoelectric receiver and
at least one support member for the piezoelectric transmitter and
piezoelectric receiver, energizing the support member and the
piezoelectric transmitter to create a scanning range over a
predetermined arc, and transceiving signals over the predetermined
arc so as receipt provides signals corresponding to a fetal
heartbeat. The support member is operatively coupled to the
piezoelectric transmitter and the piezoelectric receiver for
oscillating synchronously over a predetermined range of voltages
and frequencies and transceiving energy waves over a predetermined
angular range.
In a further embodiment of the present invention, the method
further includes the step of varying the scanning sequence. This
may be accomplished by varying the voltage input, by varying the
frequency input, or by varying the wave input. The energizing step
may be accomplished by inputting a continuous signal or a pulsed
signal. Further, the energizing step may be accomplished by
inputting several signals for progressive wave scanning.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully
from the following detailed description taken in conjunction with
the appended drawings in which:
FIG. 1 is a schematic illustration including a block diagram
illustration of the entire system;
FIGS. 2A-2C illustrate the operation of the scanning system during
continuous doppler mode;
FIG. 2D is an illustration of the scanning pattern on the mother's
abdomen;
FIGS. 3A-3C are illustrations of the component parts of the
scanning probe;
FIGS. 4A-4C illustrate the scanner. the scanning surface and the
scanning results in a different orientation;
FIG. 5 illustrates another configuration of the scanner;
FIGS. 6A-6C illustrate the operation of the scanning system during
pulsed-echo ultrasound mode;
FIGS. 7A-7D illustrate a further embodiment of the scanning system,
with an array transducer comprising multiple transmitter/receiver
elements together:
FIGS. 8A and 8B illustrate additional ways of scanning according to
further embodiments of the invention; and
FIG. 9 illustrates additional ways of scanning using progressive
scanning waves.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Reference is now made to FIG. 1, which illustrates an embodiment of
the invention, a fetal heartbeat detection system 10. System 10
comprises a scanning system 12 and a signal control and processing
system 14. Scanning system 12 functions to transmit energy waves to
a scanned area containing the fetal heart and receive reflected
waves corresponding to the fetal heartbeat. Processing system 14
signals scanning system 12 to produce energy waves and processes
signals corresponding to the received energy waves into audible
sounds corresponding to the fetal heartbeat. This allows the mother
to listen to her baby's heart.
Scanning system 12 has a piezo-ceramic plate 16 to which are
attached an energy wave transmitter 18 and an energy wave receiver
20. The transmitter 18 is made of piezoelectric material and will
oscillate in response to an electrical input. The receiver 20 is
also made of piezoelectric material and will transmit an electrical
signal based on detected mechanical waves. The transmitter 18 and
the receiver 20 are, for example, attached using an adhesive which
matches the acoustic properties of the transmitter 18 and the
receiver 20 to the piezo-ceramic plate 16. This adhesive does not
provide acoustic impedance so there is no energy loss or damping
from the adhesive. The embodiment shown illustrates transmitter 18
and receiver 20 separately configured for continuous doppler
ultrasound scanning where receiver 20 is oriented to receive
returning waves from transmitter 18, that typically diverge by an
angle of 1-3 degrees, which continuously transmits as it scans
across the mother's abdomen. Other configurations suitable for
pulsed ultrasound and a canning array are shown and described
hereinbelow with reference to FIGS. 6A-6C and 7A-7D.
The Piezo-Ceramic plate 16 is made of a piezo-ceramic material such
as Plumbum Zirconium Titanium (PZT), for example PZT-4 or PZT-5
(Morgan Matroc. Inc., Bedford, Ohio) or comparable materials from
other suppliers. The material vibrates at a frequency of 30-100
kilohertz (kHz) (in the non-audible range for people), which is the
natural frequency of piezo-plate 16, when an electric current is
applied. The mode of vibration used is the second mode according to
beam theory, as described hereinbelow. The mode of vibration is
shown schematically in FIG. 1 and designated 19, although the
orientation of transmitter 18 and receiver 20 as shown is not
illustrated in relation to the orientation of the second mode
representation, (transmitter 18 and receiver 20 are actually placed
to be always within the flat section 19a of the representation 19,
thus scanning synchronously). A silver electrode (not shown)
attached to a backing material 17 of, for example, brass of
thickness 50-200 micrometers conveys the necessary current to the
piezo-electric plate 16. Backing material 17 also adds strength to
the piezo-electric plate 16, enabling the plate 16 to be
approximately 0.2 mm thick, which in turn enables a low voltage of
approximately 2-15 V to be used to obtain the necessary vibrations.
Backing material 17 is also covered with isolating material, for
example, plastic, of approximate thickness 0.02 mm (not shown). The
voltage used decreases the chances of electric shock to the
mother.
Transmitter 18 and receiver 20 are also made of piezo-ceramic
material such as PZT-4 or PZT-8 (Morgan Matroc, Inc., Bedford,
Ohio) and typically vibrate at a natural frequency of approximately
2.5 megahertz (MHz) for the transmitter 18 and approximately
2.4-2.6 (MHz) for the receiver 20, when operating in a continuous
doppler mode as described further hereinbelow. The frequency of
vibration of the receiver 20 is approximately the frequency of
received ultrasound waves. Receiver 18 and transmitter 20 are
connected to an electric current in a similar way to the
piezo-ceramic plate 16, and vibrate in the "thickness mode of
vibration" i.e. perpendicular to the surface of the piezo-ceramic
plate 16. The matching layer 22 is made of a material, such as
plastic or indeed any other non-sound absorbent material and its
function is to be placed in contact with the mother's skin (at the
abdomen 24) when scanning takes place in order to form an interface
between the transmitter 18 and the receiver 20. The width of the
matching layer 22 (approx. 0.4 mm) is 0.25 of the wavelength of the
transmitted energy waves in order to `match` the transmitter 18 to
the mother's skin and prevent the transmitted energy waves being
damped out. The width of the transmitter 18 (approx. 0 8 mm) (i.e.,
the width of the piezo-ceramic element of the transmitter 18) is
0.5 times the wavelength of the transmitted energy waves. The
matching layer 22 also prevents the mother receiving a shock from
the piezo-ceramic plate 16, the transmitter 18 and the receiver
20.
The scanning system 12 may be divided for the purposes of
designation into two parts. The first part is a scanner 23
comprising piezo-ceramic plate 16 and matching layer 22 and the
second part is a transducer or probe 25. The probe 25 comprises the
transmitter 18 and receiver 20. The scanner 23 and probe 25
together form a scanning probe 27.
The system 10 locates and monitors the fetal heartbeat by the
placement of the scanning system 12 in the vicinity of the fetus on
the mother's abdomen 24. The scanner then locates the heartbeat by
scanning the area of the uterus within the abdomen 24 over a wide
angle with doppler ultrasound using the transmitter 18. The wide
angle scanning is achieved by applying a harmonic or pulse signal,
for example a sinusoidal wave of the natural frequency of the
scanning probe 27 to the piezo-ceramic plate 16 to cause scanning
to occur, until the fetal heartbeat is detected by the receiver 20.
The piezo-ceramic plate 16 vibrates at its natural frequency of
30-100 kHz, which is in the non-audible range for humans, as
described hereinabove. Thus, the transmitter 18 and the receiver 20
sweep a synchronized path by virtue of their attachment to the
piezo ceramic plate 16 via matching layer 22. The transmitted
energy (ultrasound) waves 26 are reflected when they encounter the
fetus heart 28 to produce the deflected energy (ultrasound) wave 30
which is received by the receiver 20. The scanning typically takes
place at a frequency of 85 kHz, in the present application, driven
by a current provided by an oscillator 32 within a processing
system 14. A second oscillator 34 provides an alternating current
that is supplied to the transmitter 18 at a frequency of, for
example, 2.5 MHz, in the present application. This causes the
production of the ultrasonic energy waves 26 towards the fetal
heart 28. The movement of the fetal heart 28 is detected by the
processing system 14 by detecting the doppler shift in frequency as
is described in greater detail hereinbelow. This shift may be
outputted as an audio output via an audio output device 29 and
speaker 31 This enables the mother to reassuringly hear her baby's
heartbeat. The doppler shift may also be outputted digitally via a
digital display 35 and counter 37.
Reference is now made to FIGS. 2A, 2B and 2C, which illustrate the
operation of scanning system 12 when configured for a continuous
doppler mode of operation. Thus, the transmitter 18 and receiver 20
are separate units allowing the transmitter 18 to transmit
continuously and the receiver 20 to be capable of receiving
continuously. FIGS. 2A, 2B and 2C illustrate when the transmitter
18 and receiver 20 are respectively oriented to scan to the central
position (zero scan angle, 1-3 degree separation between
transmitter 18 and receiver 20, see above and further hereinbelow),
when they are oriented to scan to the leftmost position, and when
they are oriented to scan to the rightmost position. Similar items
to previous figures have similar numerals and will not be described
further.
A harmonic wave of a frequency of approximately 85 kHz is applied
to the piezo-ceramic plate 16 which is anchored at each end to a
plastic casing 21. The wave applied can be of running or standing
types, and can be applied in bursts. For exemplary purposes, a
sinusoidal wave is described. The frequency applied to the
piezo-ceramic plate 16 is designed to vibrate the plate 16 in, for
example, its second mode of vibration (taking the piezo-ceramic
plate 16 as a beam anchored at two points 21). The second mode is
chosen because the flat area 19a of the graphical representation 19
(FIG. 1) readily accommodates the transmitter 18 and receiver 20 so
that they scan together. This produces a range of angular
orientations of transmitted ultrasound energy beams 26 from the
scanner 23 between the leftmost extreme of FIG. 2B and the
rightmost extreme of FIG. 2C, due to the scanning effect of the
vibrating piezoelectric plate 16. The range from the central
position, as shown in FIG. 2A is typically 10 degrees on either
side, providing a scanning arc, over a 20 degree range, but may be
as high as 20 degrees on either side, providing a scanning arc over
a 40 degree range.
It should be noted that there is a fixed angular separation of 1-3
degrees between the transmitter 18 and receiver 20 so that the
receiver 20 is in the path of the returning transmitted waves 30.
When the sinusoidal wave is a peak, the scanner is moving to or
from the middle (FIG. 2A) to the leftmost deflected position (FIG.
2B). When the sinusoidal wave is a trough, the scanner is moving to
or from the middle (FIG. 2A) to the rightmost deflected position
(FIG. 2C) with decreasing degrees of deflections in between as the
sine wave varies in amplitude FIG. 2D is a view of the scanning
pattern on the mothers abdomen 24, utilizing a sinusoidal wave,
showing the semicircular pattern of transmitted beams 26 on the
mother's skin and the position from which beams 30 are received by
the receiver 20. The semi-circular shape of the scanning pattern is
due to the exemplary semi-circular shape of transmitter 18 and
receiver 20 as described hereinbelow. Other shapes could also be
used. At the zero points of the sinusoidal wave, the scanning probe
27 will be aimed at the central position, as shown in FIGS. 2A and
2D. Thus, in all orientations, the transmitter 18 transmits energy
waves 26 at an angle to the skin of the mother and the receiver 20,
synchronized with the transmitter 18 by being mounted on the
piezo-ceramic plate 16 at the fixed relative angle described
hereinabove, is oriented to receive any returning waves 30. Thus,
the doppler shift due to the movement of the heart may be detected.
Of course, returning waves are only produced when the fetal heart
is located in the path of the transmission.
Reference is now further made to FIG. 1, which illustrates the
operation the signal control and processing system 14. A control
device 46, which may be activated by an untrained user, is utilized
to initiate oscillators 32 and 34 to produce signals in the range
of frequencies of 20-100 kHz (non-audible) and 2.5 MHz
(non-audible) respectively. The oscillators 32 and 34 cause the
transmitter 18 to transmit energy waves, and the piezo-ceramic
plate 16 to oscillate, thus produce the scanning sequence as
described hereinabove. When the fetal heart 28 encounters a
transmitted energy wave 26, the receiver 20 receives the reflected
received wave 30 with attendant doppler shift. This wave is
inputted to an amplifier 48 for amplification, mixed with the
output of the oscillator 34 in a mixer 50, passed through a
low-pass filter 52 and compared with the frequency transmitted by
the oscillator 34 by a comparator 54 to ascertain the doppler shift
which is a function of the movement of fetal heart 28 The output
from the comparator 54 is fed into a signal processor 56 and stored
in memory 58 from where it may be outputted as audio output 29 via
a speaker 31 thus enabling the mother to listen to the fetus' heart
28, or as a digital display 35 via a counter 37.
Reference is now made to FIGS. 3A-3C which illustrate the component
parts of the scanning probe 27, including the transmitter 18,
receiver 20, matching layer 22 and piezo-ceramic plate 16 with
backing material 17.
FIG. 3A is a rear view of the scanning probe 27. Similar items to
those in previous figures carry similar numerals and will not be
described further. The piezo ceramic plate 16 has, for example, a
square aperture 40 (other shapes of aperture may be utilized) cut
into it, which is not symmetrical about the axis of symmetry 45 of
the piezo-ceramic plate 16. The matching plate 22, which is glued
with non sound-absorbent acoustic adhesive (or glue) to
transmitter/receiver 25 as described hereinabove, is placed over
the square aperture 40 on the front face (not shown) of the
piezo-ceramic plate 16. The square aperture 40 has the effect of
decoupling the transmitter 18/receiver 20 from the piezo-ceramic
plate 16 in order to allow the transmitter 18 and receiver 20 to
vibrate independently.
The transmitter/receiver 25 is in the form of a circular disc 42,
which is, for example, made of plastic and is divided into two by a
central portion 44. The circular disc 42 and matching layer 22 are
formed as one unit. Piezo-ceramic material similar to that of the
piezo-ceramic plate 16 forms the transmitter 18 and receiver 20,
which are of half-disc form, are inserted into the circular disc to
freely vibrate, and are divided by central portion 44. The
transmitter 18 and receiver 20 are of thickness of 0.50 times the
wavelength to be transmitted. The central portion 44 between the
transmitter 18 and receiver 20 serves to decouple the transmitter
18 from the receiver 20 and is required to have a thickness of
approximately 0.50 times the wavelength of the transmitted energy
waves (frequency approx. 2.5 MHz, i.e., the natural frequency of
transmitter/receiver as described hereinabove). Similar independent
electrical contacts to those of the piezo-ceramic plate 16 suitably
arranged for supplying an electric current to the transmitter 18
and receiver 20 are in place. The contact points are arranged to be
on the opposite face of the transmitter 18 and receiver 20 to the
face touching matching layer 22. Isolation of the transmitter 18
from the receiver 20 is ensured by the central portion 44 between
them, as mentioned hereinabove. This ensures that the receiver 20
is free to vibrate upon receipt of energy waves 22 from the fetal
heart 28 and does not disturb the transmitter 18 and visa versa. It
should also be noted that the thickness of transmitter 18 and
receiver 20 must be less than 0.5 times the wavelength of the
natural frequency of vibration of piezo plate 16 when it is in the
second harmonic of vibration.
As mentioned above, the aperture 40 is placed asymmetric to the
axis of symmetry 45 of the piezo-ceramic plate 16. This means that
the axis of symmetry 45 divides the aperture 40 into two unequal
parts, as shown by arrows 47, 53. This creates an asymmetry of each
half of the piezo-ceramic plate 16 created by the axis of symmetry
45. This is necessary so that when the piezo-ceramic plate 16
vibrates at its natural frequency of vibration of the second
harmonic, the scanner 23 will vibrate in the second mode of
vibration according to beam theory which gives high scanning
frequencies for the input current frequencies described above. If
the second mode of vibration were not used, the input current
frequency would need to be very high to achieve the same scanning
result. More importantly, this is the most efficient form of
vibration for the scanner 23 as well as for the transmitter 18 and
receiver 20 to be integrated and scan synchronously as transmitter
18 and receiver 20 fit into area 19a of representation 19 (FIG.
1).
FIG. 3B illustrates the transmitter/receiver 25 in place within the
scanner 27. The direction of movement of the piezo-ceramic plate 16
in response to the applied alternating current is shown via the
graphical representation at the top. Each half of the plate 16
(either side of the axis of symmetry 45) moves in an opposite
direction to the other at any given moment in relation to the X and
Z axis, as shown. This is further illustrated in FIG. 3C, which
illustrates the vibrating plate 16 in this scenario.
It should be noted that if there were an asymmetry in the aperture
40 along, for example, another axis of symmetry 49 as shown in FIG.
3B, the second mode of vibration would also be exhibited in the Y-Z
direction.
Reference is now made to FIGS. 4A-C. FIG. 4A illustrates a
different orientation of piezo-ceramic material in relation to the
scanner 23, to achieve a more flexible vibration of the scanner 23
and to achieve voltage variation of the scanning angle. FIG. 4B
illustrates the scanning surface, and FIG. 4C illustrates the
scanning result on the mother's body. Similar items to those in
previous figures have similar reference numerals and will not be
described further.
Piezo-ceramic sectors 51A-51D with electrodes 55A-55D are mounted
on a backing case 41. Backing case material may be brass, for
example, with a thickness of 50-200 micrometers. The purpose of the
backing case material is to add strength to the piezo-ceramic disc
sectors 51A-51D. Thus, the sectors 51A-51D can be as thick as 0.2
mm (approximately), which allows low voltages of approximately 2-15
V to be used to obtain the necessary vibrations. The backing case
41 is also covered with isolating material such as plastic, with a
thickness of approximately 0.02 mm (not shown). The low voltage
used decreases the chances of electric shock to the mother. The
backing case 41 (typically plastic) is in the scanner 23. Aperture
40 is symmetrical to the X and Y axes.
Prior to the application of current to all four piezo-ceramic
sectors 51A-51D, their polarities may be paired in a diagonal
fashion as shown. Thus, two of the piezo-ceramic sectors 51A, 51C
have a positive polarity and the other two piezo-ceramic sectors
51B, 51D have a negative polarity on their top surface. When
current is applied, sectors 51 with the same polarity move together
in response to the applied current. This causes the movements shown
in the X-Z axis and the Y-Z axis as shown, which produces the
movement of the scanner 23 without movement of the transmitter 18,
receiver 20, matching layer 22 and circular disc 42. The exemplary
scanning pattern obtained is shown in FIG. 4C with a + or -10
degree scanning angle (resulting in a total arc of 20 degrees
scanned) obtained for the semi-circles of the transmitter 18 and
receiver 20 as shown. Thus, there is a simultaneous second mode
vibration in the X-Z and Y-Z directions.
As described hereinabove, this effect could be obtained by having
asymmetries in the aperture 40 (FIG. 3B). It should be noted that
different shapes of piezo-ceramic sectors 51 may be used, and that
the effect of different polarities may be achieved by applying
signals that differ in phase by 180 degrees. Each piezo-ceramic
sector 51 may also be independently vibrated in order to achieve a
more flexible scanning pattern.
The applied voltage may be varied in order to vary the scanning
angle using a fixed frequency. Thus, scanning can be achieved at a
variety of positive to negative angles, for example, +/-1-20
degrees. The mother or operator may thus vary the voltage using a
voltage regulator to focus on an area containing the fetal heart
28.
Reference is now made to FIG. 5 which illustrates another form of
the scanner 23, where the piezo-ceramic plate 16 is divided into
two unequal parts, (for example 60 and 62), along for example, a
diagonal axis 61. Varying the applied frequency at a constant
voltage can control the angle of scanning. This feature is
especially useful for a small device where a voltage regulator is
inappropriate. Similar items to those in previous figures have
similar reference numerals and will not be described further.
The aperture 40 is symmetrical about the axis of symmetry 45 of the
piezo-ceramic plate 16. The inequality of the two parts 60, 62 of
the piezo-ceramic plate 16 causes the scanner 23 to vibrate in the
second mode of vibration in the X-Z and Y-Z directions, which is
beneficial for the reasons described above. The scanning pattern is
achieved because there is asymmetry and consequential different
natural frequencies of vibration about the axes of symmetry 45, 49
of the plate 16 (which is now divided diagonally). The orientations
of scanning achieved by the configuration of FIG. 5 are shown
graphically with reference to the X-Z and Y-Z axes. The frequency
of the applied current may be varied by the user and by
programmable algorithms with suitable hardware and/or software.
Reference is now made to FIGS. 6A, 6B and 6C, which are
illustrations of the operation of the scanning system 12 when
configured for pulsed-echo ultrasound mode of operation. Thus, the
transmitter 18 and receiver 20 are typically a single unit,
generally designated transmitter/receiver 25, as described
hereinabove. In this unit, the transmitter/receiver 25 must
transmit and wait to receive a returning wave as per the
pulsed-echo ultrasuond technique of measuring shifts in wavelength
due to motion. The pulsed frequency is 2-6 MHz, and the change in
delay of receipt is proportional to the movement of the fetal heart
28. The transmitter/receiver 25 is one unit, configured to transmit
and then later to receive using one piezo-ceramic element.
FIGS. 6A, 6B and 6C illustrate when the transmitter/receiver 25 is
respectively oriented to scan to the zero angle position, when it
is oriented to scan to the leftmost position and when it is
oriented to scan to the rightmost position. Similar items to
previous figures have similar numerals and will not be described
further.
Scanning is achieved in a similar manner to that described
hereinabove utilizing all the types of waves described hereinabove
in relation to the first embodiment. Similar scanning angles along
arcs of +/-20 degrees are achieved.
Reference is now made to FIGS. 7A-7D, which illustrate linear or
curvilinear arrays of an ultrasound pulsed transducer. The scanning
system 12 is made up of a number of unitary transmitter/receiver 25
elements in its rightmost, middle and leftmost scanning position,
respectively. Similar items to those in previous figures have
similar reference numerals and will not be described further. The
arrangement shown enables a faster coverage of the area to be
imaged as a large number of transmitter/receiver elements 25 are
sweeping each point of the area to be imaged at a given moment. A
switching device 75 may be used to select transmitter/receiver
elements 25 to be used. Another advantage is that the area of
imaging covered by the scanner 23 may be increased. Since a large
number of transmitter/receiver elements 25 (in the order of
hundreds) may be put into the flat section 19a of the mode of
vibration representation 19 (FIG. 1), a very high resolution may be
achieved using the pulsed-echo technique for precision ultrasound
image applications. Reference is now made to FIG. 8A and FIG. 8B,
which illustrate additional ways of scanning according to further
embodiments of the present invention. Similar items to those in
previous figures have similar reference numerals and will not be
described further FIG. 8A shows a scanning probe 27 with two
piezo-ceramic plates, the original piezo-ceramic plate 16, and a
second piezo-ceramic plate 70. The first natural vibration mode of
this plate occurs, for example, at a frequency of about 40 KHz and
the second natural vibration mode of this plate occurs, for
example, at a frequency of about 80 KHz. The second piezo-ceramic
plate 70 is joined in a perpendicular fashion to the center of the
first piezo-ceramic plate 16, and a sinusoidal current, for
example, is applied to the second piezo-ceramic plate 70 in
addition to that applied to the original piezo-ceramic plate 16.
The combination of the two applied sinusoidal currents produces an
increased deflection angle of scanning due to the additional side
to side deflection of the piezo-ceramic plate 16. This is achieved
without the need for an increase in applied frequency or voltage to
the first piezo-ceramic plate 16 which would be required to achieve
the same effect without the additional piezo-ceramic plate 70. Such
an increase in frequency might be unpleasant to the user. Scanning
angles of more than +/-20 degrees can be achieved in this way.
FIG. 8B illustrates how two circular motions can assist the
scanning process. A torsional piezo-ceramic element 72 imparts a
torsional motion in addition to the motion of the piezo-ceramic
plate 16, which increases the scanning area of probe 27.
The input to the piezo-ceramic plate 16 is a sine or pulse wave, as
described hereinabove, at a resonant frequency corresponding to the
second mode of vibration of the piezo-ceramic plate, which may vary
depending on the specific dimensions and materials used. This
produces a standing wave, where all transmitter/receivers 25, are
operating in the same direction.
A scanning probe 27 with travelling-scanning waves is shown in FIG.
9. These waves are progressive, in that they are formed by an
accumulation of wave inputs. For example, backing plate 17 may be
divided into piezo-ceramic sections 74 to which sine and cosine
electrical signals are applied. This generates a progressive wave
to the right and the left in the plate 17. The matching layer 22 of
the transmitter 18 and receiver 20 moves in same direction as the
progressive wave of the plate 17.
When using progressive waves, the frequency of scanning depends on
geometrical parameters of the piezo-ceramic sections 74 rather than
on the length of the plate as is the case with standing waves, This
method allows for simplified construction and reduced dimensions,
while at the same time increasing the diagnostic area and scanning
resolution.
In general, gel is used in conjunction with ultrasound to prevent
air pockets between the skin and ultrasonic probe from changing
transmitted and received frequencies, that is, to prevent energy
loss. If a very high frequency of scanning vibration is used in
conjunction with the present invention, air pockets are expelled
preventing the need for gel.
The device described hereinabove is, of course, not limited to the
use of fetal heart monitoring but has many other applications where
a lightweight, mechanically uncomplicated scanning system is
required which is oscillating in its characteristic frequency. For
example, the system can be used for vascular applications at a
transmitter/receiver (transducer) frequency of 4-10 MHz with
similar scanner frequency and also for other medical diagnostic
applications. This may be with or without attendant transmission
and receipt of energy waves. The frequency of the piezoelement's
vibrations depends on a number of factors which include geometrical
parameters and shape as described herein, the number of electrodes
on the piezoelement and the attachment points of the piezoelement
to the fixed structure.
While preferred embodiments of the present invention have been
described, so as to enable one of skill in the art to practice the
present invention the preceding description is intended to be
exemplary only. It should not be used to limit the scope of the
invention, which should be determined by reference to the following
claims.
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